Nowadays, scanning apparatuses such as multifunction peripherals become essential electronic devices in the office or home. The multifunction peripheral has a scanning module for scanning images of documents, photographs or films. Generally, after a multifunction peripheral is turned on, a position-calibrating operation is performed to calibrate the standby position of the scanning range of the scanning module.
FIG. 1A is a schematic view illustrating a multifunction peripheral with a position-calibrating structure according to the prior art. FIG. 1B is a flowchart illustrating a method for performing a position-calibrating operation of the scanning module of the multifunction peripheral of FIG. 1A.
As shown in FIG. 1A, the conventional multifunction peripheral 1 comprises a scanning platform 10 and a scanning module 11. The scanning platform 10 has a first edge 10a and a second edge 10b, which are opposed to each other and separated from each other by a first distance D1. From the first edge 10a to the second edge 10b, the scanning platform 10 further comprises a standby position 101, a position-calibrating structure 102, a first scanning window 103 and a second scanning window 104. The position-calibrating structure 102 comprises a first rim 102a and a second rim 102b. The second rim 102b of the position-calibrating structure 102 is arranged beside the first scanning window 103. The first rim 102a of the position-calibrating structure 102 is closer to the standby position 101 than the second rim 102b. Moreover, the second rim 102b of the position-calibrating structure 102 is separated from the first edge 10a by a second distance D2. The scanning module 11 is disposed under the scanning platform 10. The scanning module 11 is driven by a motor (not shown) to be moved between the first edge 10a and the second edge 10b. 
Please refer to FIGS. 1A and 1B. Normally, after the scanning operation of the scanning module 11 is completed, the scanning module 11 is stayed at the standby position 101. After the multifunction peripheral 1 is re-started, the scanning module 11 may be moved toward the second edge 10b of the scanning platform 10 (i.e. in a first direction A) for at least a first displacement. The first displacement is substantially equal to the second distance D2. Moreover, during the scanning module 11 is moved in the first direction A, the scanning module 11 performs a scanning operation (Step S11). Then, the step S12 is performed to judge whether the position-calibrating structure 102 has been detected. If the position-calibrating structure 102 has been detected, the scanning module 11 is returned to the standby position 101 (Step S13). Meanwhile, the position-calibrating operation is completed. On the other hand, if the position-calibrating structure 102 is not detected in the step S12, the scanning module 11 is reversely moved toward the first edge 10a of the scanning platform 10 (i.e. in a second direction B) for a second displacement to assure that the scanning module 11 is returned to the left side of the position-calibrating structure 102 (Step S121). The second displacement is substantially equal to the first distance D1. Then, the step S11 is performed to move the scanning module 11 in the first direction A for approximately the second distance D2, so that the position-calibrating operation of the scanning module 11 is completed.
However, if the electricity provided to the multifunction peripheral 1 is interrupted (e.g. the utility power is interrupted or the power switch is erroneously turned off), the scanning module 11 fails to be returned to the standby position. If the scanning module 11 is stayed at the position P that is separated from the second edge 10b by a distance shorter than the second distance D2, after the multifunction peripheral 1 is re-started and the step S11 is performed, the scanning module 11 needs to be moved in the first direction A for the first displacement, which is about equal to the second direction. Under this circumstance, the scanning module 11 may hit the second edge 10b. Even if the position P is separated from the second edge 10b by a distance longer than the second distance D2, the scanning module 11 needs to be moved in the second direction B for the second displacement that is substantially equal to the first distance D1 (in the step S121). Under this circumstance, the scanning module 11 may hit the first edge 10a. 
Moreover, when the scanning module 11 is moved to the first edge 10a or the second edge 10b, the scanning module 11 fails to be advanced, but the motor continuously runs. Under this circumstance, the gear set of the motor is abraded, and thus the use life of the multifunction peripheral is shortened. In addition, the noise generated from the abrasion of the motor is uncomfortable. Moreover, even if the scanning module 11 is stayed at the first scanning window 103 and close to the position-calibrating structure 102, the steps depicted in the flowchart of FIG. 1B should be done to implement the position-calibrating operation. That is, in addition to the problems of causing noise, abrasion of the motor gear and idle running of the motor, it is also time-consuming to implement the position-calibrating operation.
Therefore, there is a need of providing a multifunction peripheral and a position-calibrating method of a scanning module so as to obviate the drawbacks encountered from the prior art.